Monday, December 28, 2020

The Ecological Disaster of Easter Island

Back in 2012 I found a good deal on flights to Easter Island, only $999 with return flight from Los Angeles.  I figured it was a once in a lifetime opportunity, so I took it.

I won't relate the entire experience here, but it was very interesting.  The Polynesians on Easter Island created a small civilization in the middle of nowhere.

Of course, one of the great stories about Easter Island is how they destroyed themselves, which is one of the great ecological disaster stories of all time. The question is, how did this ecological disaster happen? It's known that the Easter Islanders built large statues, and it's known that they chopped down all the trees on the island. Often the story is told of how they used all their trees to build their statues, and that this somehow killed them off.  Here I will provide more detail on the core elements of this famous ecological disaster.

The people of Easter Island were Polynesians who set sail from somewhere around the Marquesas Islands in the Western Pacific some time around 700-800 CE, plus or minus a few hundred years. A large two-hulled sailing ship was used, a catamaran, and was of a considerable size, possibly up to 19 meters (62ft) long and capable of carrying 12 metric tonnes (27,000lbs). This ship was sailed by a crew of colonizers and included Easter Island's legendary discoverer, Chief Hotu Matu'a. 

On board the ship they brought supplies including plants and animals that would be needed for colonization of any new island they discovered. Polynesians typically carried yams, taro, breadfruit, bananas, sugar cane, coconuts, and many other crop plants and seeds. Animals they brought typically included pigs and chickens, but it appears no pigs were brought on the voyage that discovered Easter Island. Most important for this story are the Polynesians rats that were able to stow away unnoticed in the cracks and crevices of the ship, surviving off the ship's supplies during the long voyage.

Easter Island is not a tropical paradise like other Polynesian islands of the Pacific Ocean. It lies just outside the tropical latitudes, it's not in the South Pacific high pressure zone, and it's far from the intertropical convergence zone. For this reason some of the usual Polynesians crops the first colonizers rbought withthem would not have been able to grow, for example, it is much too cold for coconuts and other tropical fruits.  Despite good rainfall and its location in the middle of the ocean, the island's humidity is 80% most of the time, which actually has an overall drying effect on the climate.  The island is also fairly new, consisting of three volcanos no older than 1 million years, which means the soil still very thin and the landscape is visibly covered with pebbles of vesicular basalt, or "cinders" as they're often called. On my visit to the island I described it as a "windswept lava grassland". Also the small size of the island and the highly porous rocks means it has no permanent streams or rivers to supply fresh water for irrigation. The only permanent fresh water on the surface of the island is contained in three lakes within each of the three main craters that form the island.

The combination of less than ideal soil, water supply, and climate, meant that farming on Easter Island was marginal.  Drying winds and poor soil forced the farmers to grow their crops inside stone circles, "manavei", so the plants wouldn't be subjected to the full force of the cool and drying winds, as well as salt spray from the waves that constantly batter the island's rocky coast. 

Since farming was marginal, the Rapa Nui people relied heavily on fishing. Tuna was the staple food of their diet.  To catch tuna required boats to go out from the shore so the tuna could be fished.

Now you can see where the problem begins. Since their arrival on the island, the Rapa Nui people had been cutting down the island's trees as fuel for fire to provide heat and cook food, to build their giant statues and other structures, and most importantly to build canoes to go fishing for their staple diet of tuna and seafood.

All the time this was going on, the rats they'd inadvertently brought to the island on their colonizing ship had been eating the seeds of the trees, so very few new trees were growing.

Eventually they chopped down all the trees and once that happened, they had no wood to build or repair boats so they could go fishing.  Without the supply of fish that was the mainstay of their diet, they starved.  War soon broke out over the remaining resources.  Some islanders desperately resorted to cannibalism

Here's my Facebook album of the trip, which is the best way to enjoy it because the photos all have captions.  

Here are the full set of original photos with no captions.

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